In the past, hot stamp foil used to make decorative foil sheets has always been a problem in the color proofing industry. Color proofing is a "cold" process. Conventional hot stamp foil will not work with this process. As a result, hot stamp foil has to be custom made at minimum run requirements. This run is usually in size 24" by 40,000' per color. This requirement offers problems which include having to stock large amounts of foil, limiting the number of colors offered because of run requirements and damage to foil sheets in re-packaging for shipping.
In order to have the foil work for the "cold" process, it must have a very easy release from the substrate thus making it very fragile to handle. These problems are passed on to the color proofers. Because the foil is "pre-coated" or made by a hot stamp foil manufacturer, the color proofer has no control over the workable qualities of the material; i.e. ease of release from the substrate, sensitivity of transferring and color intensity.
Because of the fragility of the foil, it is difficult to process an image without damage and scratching. Another problem is the need of an acid bath or caustic bath to develop the image. Critical timing is needed to avoid "under cutting" of image, which is more apparent with fine line images.
Designers want to see a specific color that will eventually be printed in a hot stamp foil. They send a swatch of the color to the color proofer to match for a rub-down transfer. The color proofer often cannot make this determination because of the limited number of foils available for this process.
Designers consider as being desirable a complete transfer with a color and foil on one piece. Also desirable would be for the color to overprint the foil. This cannot be accomplished using pre-coated foil.